Steve Dower added the comment:
> I think we should fix all the warnings, but turning this on is a great
way to make the build bots red often.

That is the obvious downside. On the other hand, we do have a very old open
issue (though I don't have the number handy) in which Guido made clear that
a build with no warnings on every possible platform would be ideal and is
desired, and this would help make sure we stay there when we reach that
point.

> I believe they already go yellow for warnings, so people are somewhat
informed, but I don't think we want to be more aggressive than that.

The individual step is colored yellow, but not the whole build. So if
you're just looking at the headings on the waterfall page, you'll never
notice. I'm not sure if we can change that setting, but that might be a
nicer solution.

> Also, I know someone who has a patch coming that fixes most of these, so
we can ignore this for a bit more and just get the fix that way if we want.

Ok, that sounds good. When that issue opens, would you mind linking it as a
dependency of this one?